common

README

common

The common package contains the expanse utility library.

Installation

As a subdirectory the main go-expanse repository, you get it with go get github.com/expanse-org/go-expanse.

Usage

RLP (Recursive Linear Prefix) Encoding

RLP Encoding is an encoding scheme used by the Expanse project. It encodes any native value or list to a string.

More in depth information about the encoding scheme see the Wiki article.

rlp := common.Encode("doge")
fmt.Printf("%q\n", rlp) // => "\0x83dog"

rlp = common.Encode([]interface{}{"dog", "cat"})
fmt.Printf("%q\n", rlp) // => "\0xc8\0x83dog\0x83cat"
decoded := common.Decode(rlp)
fmt.Println(decoded) // => ["dog" "cat"]

Patricia Trie

Patricie Tree is a merkle trie used by the Expanse project.

More in depth information about the (modified) Patricia Trie can be found on the Wiki.

The patricia trie uses a db as backend and could be anything as long as it satisfies the Database interface found in common/db.go.

db := NewDatabase()

// db, root
trie := common.NewTrie(db, "")

trie.Put("puppy", "dog")
trie.Put("horse", "stallion")
trie.Put("do", "verb")
trie.Put("doge", "coin")

// Look up the key "do" in the trie
out := trie.Get("do")
fmt.Println(out) // => verb

trie.Delete("puppy")

The patricia trie, in combination with RLP, provides a robust, cryptographically authenticated data structure that can be used to store all (key, value) bindings.

// ... Create db/trie

// Note that RLP uses interface slices as list
value := common.Encode([]interface{}{"one", 2, "three", []interface{}{42}})
// Store the RLP encoded value of the list
trie.Put("mykey", value)

Value

Value is a Generic Value which is used in combination with RLP data or ([])interface{} structures. It may serve as a bridge between RLP data and actual real values and takes care of all the type checking and casting. Unlike Go's reflect.Value it does not panic if it's unable to cast to the requested value. It simple returns the base value of that type (e.g. Slice() returns []interface{}, Uint() return 0, etc).

Creating a new Value

NewEmptyValue() returns a new *Value with it's initial value set to a []interface{}

AppendList() appends a list to the current value.

Append(v) appends the value (v) to the current value/list.

val := common.NewEmptyValue().Append(1).Append("2")
val.AppendList().Append(3)

Retrieving values

Get(i) returns the i item in the list.

Uint() returns the value as an unsigned int64.

Slice() returns the value as a interface slice.

Str() returns the value as a string.

Bytes() returns the value as a byte slice.

Len() assumes current to be a slice and returns its length.

Byte() returns the value as a single byte.

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
val.Get(0).Uint() // => 1
val.Get(1).Str()  // => "2"
s := val.Get(2)   // => Value([]interface{}{3})
s.Get(0).Uint()   // => 3

Decoding

Decoding streams of RLP data is simplified

val := common.NewValueFromBytes(rlpData)
val.Get(0).Uint()

Encoding

Encoding from Value to RLP is done with the Encode method. The underlying value can be anything RLP can encode (int, str, lists, bytes)

val := common.NewValue([]interface{}{1,"2",[]interface{}{3}})
rlp := val.Encode()
// Store the rlp data
Store(rlp)

Documentation

Overview

Package common contains various helper functions.

Index

• Constants
• Variables
• func AbsolutePath(Datadir string, filename string) string
• func Bytes2Hex(d []byte) string
• func CopyBytes(b []byte) (copiedBytes []byte)
• func EmptyHash(h Hash) bool
• func FileExist(filePath string) bool
• func FromHex(s string) []byte
• func HasHexPrefix(str string) bool
• func Hex2Bytes(str string) []byte
• func Hex2BytesFixed(str string, flen int) []byte
• func IsHex(str string) bool
• func IsHexAddress(s string) bool
• func LeftPadBytes(slice []byte, l int) []byte
• func LoadJSON(file string, val interface{}) error
• func MakeName(name, version string) string
• func PrintDepricationWarning(str string)
• func Report(extra ...interface{})
• func RightPadBytes(slice []byte, l int) []byte
• func ToHex(b []byte) string
• type Address
  • func BigToAddress(b *big.Int) Address
  • func BytesToAddress(b []byte) Address
  • func HexToAddress(s string) Address
  • func StringToAddress(s string) Address
  • func (a Address) Big() *big.Int
  • func (a Address) Bytes() []byte
  • func (a Address) Format(s fmt.State, c rune)
  • func (a Address) Hash() Hash
  • func (a Address) Hex() string
  • func (a Address) MarshalText() ([]byte, error)
  • func (a *Address) Set(other Address)
  • func (a *Address) SetBytes(b []byte)
  • func (a *Address) SetString(s string)
  • func (a Address) Str() string
  • func (a Address) String() string
  • func (a *Address) UnmarshalJSON(input []byte) error
  • func (a *Address) UnmarshalText(input []byte) error
• type Hash
  • func BigToHash(b *big.Int) Hash
  • func BytesToHash(b []byte) Hash
  • func HexToHash(s string) Hash
  • func StringToHash(s string) Hash
  • func (h Hash) Big() *big.Int
  • func (h Hash) Bytes() []byte
  • func (h Hash) Format(s fmt.State, c rune)
  • func (h Hash) Generate(rand *rand.Rand, size int) reflect.Value
  • func (h Hash) Hex() string
  • func (h Hash) MarshalText() ([]byte, error)
  • func (h *Hash) Set(other Hash)
  • func (h *Hash) SetBytes(b []byte)
  • func (h *Hash) SetString(s string)
  • func (h Hash) Str() string
  • func (h Hash) String() string
  • func (h Hash) TerminalString() string
  • func (h *Hash) UnmarshalJSON(input []byte) error
  • func (h *Hash) UnmarshalText(input []byte) error
• type PrettyDuration
  • func (d PrettyDuration) String() string
• type StorageSize
  • func (self StorageSize) Int64() int64
  • func (self StorageSize) String() string
• type UnprefixedAddress
  • func (a UnprefixedAddress) MarshalText() ([]byte, error)
  • func (a *UnprefixedAddress) UnmarshalText(input []byte) error
• type UnprefixedHash
  • func (h UnprefixedHash) MarshalText() ([]byte, error)
  • func (h *UnprefixedHash) UnmarshalText(input []byte) error

Constants

const (
	HashLength    = 32
	AddressLength = 20
)

Variables

var (
	Big1   = big.NewInt(1)
	Big2   = big.NewInt(2)
	Big3   = big.NewInt(3)
	Big0   = big.NewInt(0)
	Big32  = big.NewInt(32)
	Big256 = big.NewInt(0xff)
	Big257 = big.NewInt(257)
)

Common big integers often used

Functions

func AbsolutePath

func AbsolutePath(Datadir string, filename string) string

func Bytes2Hex

func Bytes2Hex(d []byte) string

func CopyBytes

func CopyBytes(b []byte) (copiedBytes []byte)

Copy bytes

Returns an exact copy of the provided bytes

func EmptyHash

func EmptyHash(h Hash) bool

func FileExist

func FileExist(filePath string) bool

func FromHex

func FromHex(s string) []byte

func HasHexPrefix

func HasHexPrefix(str string) bool

func Hex2Bytes

func Hex2Bytes(str string) []byte

func Hex2BytesFixed

func Hex2BytesFixed(str string, flen int) []byte

func IsHex

func IsHex(str string) bool

func IsHexAddress

func IsHexAddress(s string) bool

IsHexAddress verifies whether a string can represent a valid hex-encoded Ethereum address or not.

func LeftPadBytes

func LeftPadBytes(slice []byte, l int) []byte

func LoadJSON

func LoadJSON(file string, val interface{}) error

LoadJSON reads the given file and unmarshals its content.

func MakeName

func MakeName(name, version string) string

MakeName creates a node name that follows the ethereum convention for such names. It adds the operation system name and Go runtime version the name.

func PrintDepricationWarning

func PrintDepricationWarning(str string)

PrintDepricationWarning prinst the given string in a box using fmt.Println.

func Report

func Report(extra ...interface{})

Report gives off a warning requesting the user to submit an issue to the github tracker.

func RightPadBytes

func RightPadBytes(slice []byte, l int) []byte

func ToHex

func ToHex(b []byte) string

Types

type Address

type Address [AddressLength]byte

Address represents the 20 byte address of an Ethereum account.

func BigToAddress

func BigToAddress(b *big.Int) Address

func BytesToAddress

func BytesToAddress(b []byte) Address

func HexToAddress

func HexToAddress(s string) Address

func StringToAddress

func StringToAddress(s string) Address

func (Address) Big

func (a Address) Big() *big.Int

func (Address) Bytes

func (a Address) Bytes() []byte

func (Address) Format

func (a Address) Format(s fmt.State, c rune)

Format implements fmt.Formatter, forcing the byte slice to be formatted as is, without going through the stringer interface used for logging.

func (Address) Hash

func (a Address) Hash() Hash

func (Address) Hex

func (a Address) Hex() string

Hex returns an EIP55-compliant hex string representation of the address.

func (Address) MarshalText

func (a Address) MarshalText() ([]byte, error)

MarshalText returns the hex representation of a.

func (*Address) Set

func (a *Address) Set(other Address)

Sets a to other

func (*Address) SetBytes

func (a *Address) SetBytes(b []byte)

Sets the address to the value of b. If b is larger than len(a) it will panic

func (*Address) SetString

func (a *Address) SetString(s string)

Set string `s` to a. If s is larger than len(a) it will panic

func (Address) Str

func (a Address) Str() string

Get the string representation of the underlying address

func (Address) String

func (a Address) String() string

String implements the stringer interface and is used also by the logger.

func (*Address) UnmarshalJSON

func (a *Address) UnmarshalJSON(input []byte) error

UnmarshalJSON parses a hash in hex syntax.

func (*Address) UnmarshalText

func (a *Address) UnmarshalText(input []byte) error

UnmarshalText parses a hash in hex syntax.

type Hash

type Hash [HashLength]byte

Hash represents the 32 byte Keccak256 hash of arbitrary data.

func BigToHash

func BigToHash(b *big.Int) Hash

func BytesToHash

func BytesToHash(b []byte) Hash

func HexToHash

func HexToHash(s string) Hash

func StringToHash

func StringToHash(s string) Hash

func (Hash) Big

func (h Hash) Big() *big.Int

func (Hash) Bytes

func (h Hash) Bytes() []byte

func (Hash) Format

func (h Hash) Format(s fmt.State, c rune)

Format implements fmt.Formatter, forcing the byte slice to be formatted as is, without going through the stringer interface used for logging.

func (Hash) Generate

func (h Hash) Generate(rand *rand.Rand, size int) reflect.Value

Generate implements testing/quick.Generator.

func (Hash) Hex

func (h Hash) Hex() string

func (Hash) MarshalText

func (h Hash) MarshalText() ([]byte, error)

MarshalText returns the hex representation of h.

func (*Hash) Set

func (h *Hash) Set(other Hash)

Sets h to other

func (*Hash) SetBytes

func (h *Hash) SetBytes(b []byte)

Sets the hash to the value of b. If b is larger than len(h), 'b' will be cropped (from the left).

func (*Hash) SetString

func (h *Hash) SetString(s string)

Set string `s` to h. If s is larger than len(h) s will be cropped (from left) to fit.

func (Hash) Str

func (h Hash) Str() string

Get the string representation of the underlying hash

func (Hash) String

func (h Hash) String() string

String implements the stringer interface and is used also by the logger when doing full logging into a file.

func (Hash) TerminalString

func (h Hash) TerminalString() string

TerminalString implements log.TerminalStringer, formatting a string for console output during logging.

func (*Hash) UnmarshalJSON

func (h *Hash) UnmarshalJSON(input []byte) error

UnmarshalJSON parses a hash in hex syntax.

func (*Hash) UnmarshalText

func (h *Hash) UnmarshalText(input []byte) error

UnmarshalText parses a hash in hex syntax.

type PrettyDuration

type PrettyDuration time.Duration

PrettyDuration is a pretty printed version of a time.Duration value that cuts the unnecessary precision off from the formatted textual representation.

func (PrettyDuration) String

func (d PrettyDuration) String() string

String implements the Stringer interface, allowing pretty printing of duration values rounded to three decimals.

type StorageSize

type StorageSize float64

func (StorageSize) Int64

func (self StorageSize) Int64() int64

func (StorageSize) String

func (self StorageSize) String() string

type UnprefixedAddress

type UnprefixedAddress Address

UnprefixedHash allows marshaling an Address without 0x prefix.

func (UnprefixedAddress) MarshalText

func (a UnprefixedAddress) MarshalText() ([]byte, error)

MarshalText encodes the address as hex.

func (*UnprefixedAddress) UnmarshalText

func (a *UnprefixedAddress) UnmarshalText(input []byte) error

UnmarshalText decodes the address from hex. The 0x prefix is optional.

type UnprefixedHash

type UnprefixedHash Hash

UnprefixedHash allows marshaling a Hash without 0x prefix.

func (UnprefixedHash) MarshalText

func (h UnprefixedHash) MarshalText() ([]byte, error)

MarshalText encodes the hash as hex.

func (*UnprefixedHash) UnmarshalText

func (h *UnprefixedHash) UnmarshalText(input []byte) error

UnmarshalText decodes the hash from hex. The 0x prefix is optional.